1. Field of the Invention
This invention relates to release devices for releasing a chemical vapor into a space over an extended period of time.
2. State of the Art
Treatment of storage facilities with chemicals of various types has been practiced in various agricultural businesses. The treatment may be with chemical vapors, dusts, powders or the like, such as the treatment of potato storage facilities with sprout inhibiting chemicals.
Considerable study and innovation have been directed towards inhibition of potato sprouting during storage in large storage facilities. U.S. Pat. No. 2,341,868; to Hitchcock et al., Luck, U.S. Pat. No. 4,078,480; Vaughn, et al., U.S. Pat. No. 5,129,951; Morgan, 4,887,525; and Plant, U.S. Pat. No. 3,128,170 describe various treatments to prevent sprouting in storage facilities.
Potatoes when being dug are frequently bruised, cut and/or abraded. These injuries to the potatoes oftentimes cause spoilage during shipment, storage and the like. A process known as suberization occurs naturally which tends to heal many of these injuries. However, whenever potatoes are stored, which occurs with a particularly large portion of potatoes harvested in any given year, if healing occurs slowly, a significant loss of potatoes can occur through spoilage. Early treatment with certain sprout inhibitors, such as CIPC, may retard the suberization process, thus contributing to the loss of potatoes through spoilage.
For example, it is relatively common in the potato storage industry to treat potatoes with Chloroisopropyl-N-carbamate (CIPC) to prevent or retard development of sprouts in the potatoes. Even though untreated potatoes are stored at a cool temperature, for example, generally between about 40.degree. and 45.degree. F., sprouting does begin to occur after a month or more of storage. Storage of upwards of six to eight months is typical for a stored potato harvest. Thus, without treatment of a chemical such as CIPC, the stored potatoes become entangled in sprouts and the whole stored lot of potatoes may become economically useless. Although early treatment with CIPC could be advantageous for sprout inhibition purposes, application of CIPC is typically delayed until after suberization has occurred inasmuch as CIPC tends to retard suberization, resulting in accelerated rot and spoilage.
Testing of isomers of dimethyl naphthalene (DMN) as a potential sprout inhibitor was conducted by placing alumina particles containing DMN in a box of potatoes stored at 10.+-.0.5.degree. C. in a ventilated cooler for a period of 12 weeks. The potatoes evidenced sprout inhibition in comparison with a control batch, i.e., in an untreated batch, and with a batch treated with Tecnazene, a commercial sprout inhibitor. Beveridge, et al., The Assessment of Some Volatile Organic Compounds as Sprout Suppressants for Ware and Seed Potatoes, Potato Res. 24 (1981) 61-76 and Beveridge, et al., Dimethyl Naphthalene as a Sprout Suppressant for Ware and See Potatoes, Potato Res., 24 (1981) 77-88.
The use of DMN treatment in a large storage facility has also been proposed. In PCT application PCT/GB92/01482 (Int'l. Pub. No. WO 93102563) of Everett-Todd, a system for monitoring the vapor pressure of alkyl naphthalenes is disclosed wherein alkyl naphthalenes are added to the facility when the monitored vapor pressure of alkyl naphthalenes falls below a certain value, e.g., 5 mg of alkyl naphthalene per cubic meter of storage free space.
While considerable effort has been devoted to sprout prevention of potatoes stored in larger facilities, little or no effort has been devoted to prevention of sprouting of potatoes during shipment. Freshly-dug and stored potatoes are shipped to commercial markets, e.g., restaurants and the like, and to consumer markets, e.g., retail grocery stores, in refrigerated trailers and railroad cars. No other particular effort has been made to inhibit sprouting during the shipping and distribution process.